The VASE setup shines linearly polarized light on the sample surface with different angles of incidence. The electric field vector is oriented obliquely with respect to the plane of the light incidence. Then the ellipticity of the reflected light from the sample surface (which obviously appears in the case of the oblique incidence as one can see from the Fresnel-Airy formulas) is analyzed for the s-polarized component of the electric field vector (component in the plane of incidence) and p-polarized component(that orthogonal to the incidence plane). The
measures the ratio of the s and p components for different angles and the existing softwares[19] fit the angular dependence of these results to the mathematically generated model of this angular dependence expected for a uniaxial layer of given thickness. This fitting deliversthe most suitable values of both components of the complex permittivity tensor at a given wavelength. Since the data is measured over the entire wavelength range the analysis of the frequency dispersion of the permittivity allows one to judge on the applicability of the VASE technique to the given nanostructure. If the dispersion turns out to be non-physical,i.e. violates physical limitations[4], the method is not applicable. For natural films it was checked that the VASE retrievalis very accurate even near the absorption peaks where the dispersion of permittivity appears[20]. Therefore it should be applicable also for electromagnetic characterization of isotropic and uniaxial nanostructured layers beyond the resonance of its constitutive elements. Instructions of the usage can be found in the Internet [21].
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